Select one of the four surfaces from the pull-down menu. Parametric equations for the surface are shown at the right. Use the mouse to drag the red vertical line, u equals au=a, or the blue horizontal line, v equals bv=b, in the u vuv-plane. The corresponding grid curve on the surface will move accordingly. You may wish to rotate the axes of the 3D graph with the mouse for different views of the surfac and its grid curves.
For each surface, how would you describe the family of grid curves with uu constant? With vv constant?